Outboard motors are powered by engines which are positioned within a cowling. The engine includes an output shaft which extends therefrom. The engine is oriented such that the output shaft extends downwardly to a lower drive section of the outboard motor for driving a propeller.
These engines include a lubricating system for delivering lubricating oil throughout the engine. Typical engine lubrication systems include a pump for delivering oil through oil delivery lines to various parts of the engine. Oil returns by gravity to an oil sump, from which it is drawn by the pump and returned to the engine.
In situations where the engine is oriented such that its output shaft extends horizontally, as compared to vertically, the oil sump is conveniently positioned below the engine block in a plane generally parallel to the output shaft. Oil flows downwardly through the engine to the sump, and the pump pumps the oil back up into the engine.
Orientation of the engines in outboard motors such that their output shafts extend vertically downward complicates the positioning of the oil sump. If the oil sump is connected to the engine block as described above, when the engine is rotated such that its output shaft extends vertically, the oil sump becomes oriented along the side of the engine in a vertical plane. This orientation is generally impermissible, since the oil will not drain back into the sump from the engine via gravity. In addition, it is generally desirable to limit the size of the outboard motor, especially in the horizontal direction. When the oil sump is positioned along the side of the engine, the engine's size in the horizontal direction is increased.
So that the oil will drain from the engine back to the oil sump by gravity, and to limit the engine's outward dimension, the oil sumps of engines powering outboard motors generally comprise chambers positioned below the end of the engine within the lower drive portion of the motor cowling. As the output shaft extends vertically downward in the same area in which it is desirable to position the oil sump, the oil sump often comprises a relatively narrow, but elongate chamber positioned alongside the output shaft. Because the oil pump inlet is positioned at the bottom of the sump, sump designs which have their ends far below the engine have the disadvantage that the oil pump must pump the oil a great distance upwardly into the engine, drawing greater engine power and/or generally lowering the oil pressure within the engine.
Another problem generally associated with these oil pumps is that the pumping or working elements thereof are positioned in a pump housing. The entire pump is then normally positioned within another portion of the engine, such as within the oil sump itself. This makes it difficult to service the oil pump, as the oil pump must first be located and then the outer housing thereof must be removed.
It is, therefore, an object of the present invention to provide an improved oil pump. It is a further object of the invention to provide an oil pump for the engine of an outboard motor wherein the oil pump is positioned close to the engine. It is yet a further object of the invention to provide an oil pump which is readily serviceable.